A common example of fabric processing is dyeing. In such a process, woven or non-woven fabric is usually soaked in a solution in which a coloring agent such as a dye is dissolved or dispersed, so that the coloring agent is able to diffuse into and adsorb onto the fabric. In order to achieve high color fastness, distributing a coloring agent through fabric is desirable for most dyeing processes.
Water has conventionally been used as a solvent in most dyeing processes. As a result, the dyeing industry consumes a large amount of water. Further, the processes to prepare the fiber before dyeing such as bleaching and whitening also consume a large amount of water. This water usage also results in the problem of pollution in water environments. It is desirable to reduce the amount of water used and/or the amount of waste liquid produced, and optionally that coloring agents and/or other components are able to be reused.
Further, fabrics to be dyed include those made by weaving fibers and those having uneven properties (e.g., uneven hydrophilicity). As it is difficult for such fabrics to be dyed evenly, a technique using a dyeing assistant may typically be used. In the technique, a solution for dyeing is made by way of mixing the dyeing assistant and a solvent containing a large amount of high-concentration coloring agent so as to evenly dye the fabric. This technique causes a large amount of coloring agent to remain in the waste liquid without being used for dyeing, further increasing the environmental burden of the industrial process.